Landslides in the Sydney Basin - Geoscience Australia

Seismic Hazard in SydneyProceedings of the one day workshopThe Inner Sydney Basin: Geology, LandSurface and EarthquakesDAVID BRANAGANSchool of Geosciences, University of SydneyABSTRACTThe term Sydney Basin is often misunderstood by the general public, who think it refers to theregion extending to the edge of the Blue Mountains, north to the Hawkesbury River and south toabout Picton. This Inner Sydney Basin is the focus of discussion in this paper. While the LapstoneStructural Complex is given most attention as a possible site for strong seismicity, numerous smallerfault zones, such as the Coastal and Berowra Waters lineaments, also need to be studied. Althoughsome geophysical evidence has been put forward that the Lapstone structures have developed bythrusting from the west, the general pattern of the complex, its extension north and south and therelated structures at these extremities are more consistent with normal faulting, and down draggingof the Cumberland Basin.INTRODUCTIONThis paper discusses some aspects of what I call the Inner Sydney Basin, the region extendingapproximately north to the Hawkesbury River, south to Stanwell Park and west to the lower BlueMountains (Figure 1).Figure 1. The “Inner Sydney Basin”, what many lay people regard as the total Sydney Basin(Branagan, 1985).This is what the general public think of when the term ‘Sydney Basin” is used, although it isapproximately what geologists define as the Cumberland Basin, with the adjacent plateaux. Whilethe discussion of this paper focuses on this inner region, it needs to be remembered that earthquakes,7